• synonyms


noun Biochemistry.
  1. an amino acid, H2N(CH2)3CH(NH2)COOH, obtained by the hydrolysis of arginine and occurring as an intermediate compound in the urea cycle of mammals.
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Origin of ornithine

1880–85; ornith(uric acid), secreted by birds + -ine2
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

British Dictionary definitions for ornithine


  1. an amino acid produced from arginine by hydrolysis: involved in the formation of urea in the liver; diaminopentanoic acid. Formula: NH 2 (CH 2) 3 CHNH 2 COOH
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Word Origin for ornithine

C19: from ornithuric (acid) secreted in the urine of birds, from ornitho- + uric
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

ornithine in Medicine


  1. An amino acid formed by the hydrolysis of arginine and important in the formation of urea.
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The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

ornithine in Science


  1. An amino acid not found in proteins, formed by hydrolyzing arginine and important in the formation of urea. Chemical formula: C5H12N2O2.
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The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.